My wife and I are leaving for China (for visit) soon. Her green card expires 3/30. We will be back 3/25. We are leaving 2/29. So we'll be out of the country for 25 days. Should we mail in the i-751 right before we leave, say on 2/28. Or should we mail it in after we come back on 3/26? The only problem with mailing it in on 2/28 is that we might be scheduled to show up before we return from China. Any one familar with the timeline? Thanks, Jin P.S. I have heard about the stamp (for returning). But we have decided to hold the actual green card to avoid any trouble for returning.